With atmospheric CO2 concentrations reaching the 400 ppm level, the media and a number of alarmist scientists have set off the mega-alarm bells, claiming “record high levels” of CO2 had been reached, and that the planet is on the verge of an overdose. This is based purely on ignorance of the Earth’s history.

Worrying that 400 ppm is too high is like worrying about your fuel tank overflowing when it reaches the 1/8 mark during filling.

From a historical perspective, an atmospheric CO2 concentration of 400 ppm is actually almost scraping the bottom of the barrel. Over the Earth’s history, atmospheric CO2 concentrations have ranged from 180 ppm to 7000 ppm, see Figure 1 below. On that scale we are in fact today barely above the Earth’s record lows.

Figure 1: Atmospheric CO2 concentration is just barely above the life-sustaining levels of 150 ppm. For life to have real buffer against mass extinction, CO2 needs to be closer to 1000 ppm. Source: http://deforestation.geologist-1011.net/.

That 400 ppm is actually dangerously low is a fact the alarmists keep avoiding and suppressing. Below 150 ppm, plant-life dies off on a massive scale. The Earth actually came very close to that point many times over the last 2 million years during the ice ages. At the bottom of the last ice age just 20,000 years ago, life on the planet literally teetered on the brink when CO2 fell to a level of just 180 ppm. Do we really want to live on the brink of extinction?

It’s a fact that biologists have shown that once the atmospheric CO2 level falls below the 500 ppm level, plants really begin to suffer. Many of us have seen the video showing how plants grow faster under higher CO2 concentrations. The following charts show the growth curves of some plants as a function of CO2 concentration:

Note that at high CO2 concentrations, such as 800 ppm, plants thrive. But as CO2 levels fall off, growth rates really start to plummet once they fall below 500 ppm. History shows that the Earth sustains much more life, i.e. is much greener and fruitful, when CO2 levels are higher, i.e. in the vicinity of 1000 ppm.

No one disputes that man’s activities have helped to increase atmospheric CO2 concentration, and it should not be in dispute that plants and life on the planet are thankful that man has done so. At 400 ppm, the planet is a safer place to be and will be even safer at 1000 ppm.

12 responses to “Atmospheric CO2 Concentrations At 400 PPM Are Still Dangerously Low For Life On Earth”

As far as I know, C3 plants stop photosyntheiszing under 150 ppm, while C4 plants (grases) can go on straight to 0 ppm. That’s basically the reason C4 plants are so widespread; they were able to take advantage of periods of CO2 scarcity. The C4 cycle is less efficient so when there’s enough CO2 C3 plants win out.

Having spend the some time reading about banana ripening facilities, I think the answer is 1%. In banana ripening facilities, they have to extract CO2 which is produced during the ripening process, to below levels of 1% to ensure ripening takes place. Google banana ripening and read the Hawaiian universities excellent guidelines to the banana industry. This figure of 1% CO2 is also repeated by the Australian avocado ripening industry guidelines, for the very same reason as in the banana ripening industry, it stops avocados from ripening.

One percent CO2 is 10000ppm, so we have a reasonable margin from 400ppm to get to 10000ppm when our crops will stop ripening in the fields. Maybe we started to panic a couple of millennia too soon.

“400 ppm of carbon dioxide in the atmosphere should remind us of our continuing success at expanding the global supply of energy to meet a growing demand. That success which ultimately leads to an improvement of the global standard of living and a reduction in vulnerability to the vagaries of weather and climate. 400pm is cause for celebration. ‘A world lit only by fire’ is not,” they concluded.

Some plants grow faster under higher CO2 concentrations but at a cost: protein concentrations in the tissues of these plants decrease and so do minerals of nutritional importance including calcium, magnesium and phosphorus. So while crop yields might increase, the quality of the crop decreases and so animals feeding on these crops will need to eat more of them to compensate for the loss of nutrients.

As someone else has pointed out, C4 plants do not benefit at all with elevated CO2. These plants include important crops like maize, sugar cane, sorghum and millet. There are fewer C4 species but they occupy a large area on Earth. The enormous tropical grasslands of Africa and South America are C4 plants and these will not benefit much from elevated CO2.